The present application relates to analytical instruments, and more particularly to methods and techniques for calibrating analytical instruments to permit their use for analyzing materials having non-flat, repeating surface patterns. The application is particularly suited to fluorescence measurement of non-flat surfaces with repeating patterns such as welding wire, but may also be implemented for other appropriate applications.
One particular fluorescence technique known as X-ray fluorescence analysis is used to identify elements and the concentration of elements, which comprise a material under investigation. This and similar techniques involve irradiating an area with a high energy beam, such as X-rays, gamma rays, neutrons or particle beams and observing the resulting fluorescence emitted by the irradiated area.
Such systems generally include a source of excitation radiation, an optic for directing the radiation toward a sample, a radiation detector to detect the stimulated fluorescence emissions from the sample (possibly through another optic), and a display for displaying the spectral output.
In X-ray fluorescence spectroscopy, for example, as the excitation photons strike the sample, they knock electrons out of their orbits around the nuclei of the atoms in the sample, creating vacancies that destabilize the atoms. The atoms stabilize when electrons from the outer orbits are transferred to the inner orbits. These atoms emit a characteristic X-ray fluorescence photon representing the difference between the two binding energies of the corresponding orbits. The detector collects this spectrum of photons and converts them to electrical impulses proportional to the energies of the various X-rays in the sample's spectrum. Since each element has a different and identifiable X-ray fluorescence signature, an operator can determine the presence and concentration of the element(s) within the sample by reviewing specific areas of the emitted spectrum.
While X-ray fluorescence spectroscopy has been employed as a tool in many industries where rapid, repeatable elemental measurements of materials are useful, the state of the current technology does not sufficiently support the capability of analyzing non-flat surfaces. Rather, existing analysis techniques require the surface of the sample presented to the spectrometer have a flat surface in order to perform highly accurate analysis. This becomes a particular limitation in those industries where the materials to be analyzed do not commonly have a flat surface, or where it is quite difficult to modify the sample to yield a flat area for analysis. One particular situation where such measurements become difficult is in the measurement of rods, wires or electrodes used in the welding industry.
This problem is compounded when an organization employs multiple analytical devices. In view of these issues, it would be beneficial to calibrate analytical devices to accurately measure non-flat samples, and to achieve consistent readings of non-flat samples among multiple analytical devices.
Therefore, it is considered useful to provide an improved calibration technique and system which permits for the calibration of analytical instruments, such as spectrometers, for analysis of samples having non-flat repeating surfaces, and to extend the calibration technique to multiple analytical instruments of the same type. It would also be useful for the technique to be designed for use where a user does not need to know the actual concentration of elements of a sample material, to produce materials having appropriate characteristics.